Time-limit circuit-breaker.



Patented Aug. 5,. I902.

H. Mf-HOBART.

TIME LIMIT CIRCUIT BREAKER.

(Application filed Jan. 5, 1901.)

(No Model.)

LB, mm m WM 5 m H m Witnesses v UNITED STATES PATENT OEEIcE.

HENRY M. HOBART, OF BERLIN, GERMANY, ASSIGNOR TO GENERAL ELEC- TRIC COMPANY, A CORPORATION OF NEW YORK.

TIME-LIMIT CIRCUIT-BREAKER.

SPECIFICATION forming part of Letters Patent No. 706,055, dated August 5, 1902.

Application filed January 5, 1901- Serial No. 42,260. (No model.) I

To all whom it may concern.-

Be it known that I, HENRY M. HOBART, a citizen of the United States, residing at Berlin, Germany, have invented certain new and useful Improvements in Time-Limit Circuit- Breakers, (Case No. 1,942,) of which the following is a specification.

In many cases it is desirable that circuitbreaking devices should not operate on heavy 1o loads of only a few seconds or a fraction of a second duration.

My present invention consists of a circuitbreaker so arranged as to respond to an overload only after the overload has lasted a predetermined time. To accomplish this mode of operation, I arrange the tripping-coil of the circuit-breaker in a divided circuit the branches of which are of difierent time constants and are connected to the circuit upon which the circuit-breaker operates; In the branch containing the tripping-coil is placed a device of such construction as to retard the growth of current in this branch when the current in the main circuit varies. The

2 5 other branch of the divided circuit is formed so as to offer. no impediment either to the growth or decay of rapidly-varying currents. The result of this arrangement is that when the current in the main circuit suddenly increases the portion of the same passing through the tripping-coil increases but slowly, while that in the branch circuit about the tripping-coil rises instantly to its full value. Unless the main current is maintained for 3 5 a predetermined interval, for which the parts are proportioned, the circuit-breaker will fail to act, the main current returning to a value or values below that for which the circuitbreaker is set. In case, however, the overload-current lasts a length of time sufficient to allow the current in the tripping-coil branch to rise to a steady value the circuit-breaker will then operate My invention may be better understood by 5 reference to the following description, taken in connection with the accompanying draw ings, in which- Figure'l represents the invention in diagram, and Fig. 2 shows a detail.

The scope of the invention is not to be limited by anything which I have said in doscribing the same, but is to be determined by reference to the claims appended hereto.

In the drawings I have represented at la tripping circuit-breaker of atype well-known 5 5 in the art. This circuit-breaker consists of two toggle-arms 2 and 3, the upper one, 8, carrying a bridging contact 4, cooperating with the fixed contacts 5to open or close acircuit 6 7. The lower toggle-arm 2 is pivoted at 8 to a supporting-frame. (Not shown.) An operating-handle permits the resetting of the circuit-breaker, the operation consisting of a downward pull on the handle, which acts to throw in the knuckle of the toggle-joint and bring the bridging contact linto engagement with the cooperating fixed contacts 5. A pivoted latch 10 retains the parts in this position until the current in the tripping-coil 11, which acts upon this latch, is sufficient to trip the circuit-breaker and open the circuit 6 7.

Instead of placing the tripping-coil 11 directly in series with the main circuit, as is usual in practice, I include the same in one branch of a divided circuit, in series with which branch I place a reactance devicesuch, for example, as an inductance-coil. The other branch of the divided circuit consists of such a construction as will allow the current therein to rise and fall rapidly in respouse to variation in the differences of potential between its terminals. The circuit may therefore consist of a non-inductive resistance o1": comparatively low value. In the drawings this low-resistance branch is indicated at 12. The other branch in parallel therewith includes the tripping-coil 11 of the circuit-breaker and a device, such as an inductance-coil 13, in series therewith. This inductance-coil may consist of windings placed 0 about an iron core; but, if desired, I may in order to obtain the same effect use instead a system of iron bars, as shown in Fig. 2, of considerable cross section and of proper length. Any sudden rush of current through 9 5 conductors of this character would take place in such a manner as to cause a concentration of current about the surface of the bar or bars, this concentration of current being known in the art as the skin eifect. As a result of this peculiar distribution of current the growth of the same to its full value is very much retarded. The alternative path about the tripping-coil carries more than the usual proportion of the current until the normal condition of steadiness is again reached. If the overload or rush of current lasts long enough to enable the current in the trippingcoil branch to rise to a steady value, the circuit-breaker will operate; otherwise not.

In the above description I have described my invention in connection with a tripping circuit-breakerof one particular type; but it is not to be understood that I thereby limit my invention to use in connection With a circuit-breaker of such construction, since it is applicable to circuit-breakers of many other kinds and descriptions. In other details my invention is capable of various modifications, and for that reason I do not wish my claims limited to the particular construction shown.

What I claim as new, and desire to secure by Letters Patent of the United States, is-

1. The combination with a circuit-breaker having a tripping-coil normally connected to the circuit upon which the circuit-breaker operates, of electroreactive means for causing the current in said tripping-coil to Vary slower than the current in said circuit.

2. The combination of a divided circuit, one branch of Which includes the tripping-coil of a circuit-breaker, and a device possessing ind uctance in series with said trippingcoil.

3. The combination of a divided circuit, one branch 01": which includes the tripping-coil of a circuit-breaker, and a device in series with said tripping-coil and acting to oppose variation of current but inactive during a steady condition of current.

4-. A circuit-breaker comprising circuit-in-- terrupting means, a tripping-coil, and a device possessing reactance for preventing the current in the tripping-coil from varying at the same rate as the current in the circuit upon which the circuit-breaker operates.

5, The combination of a divided circuit, one branch of which includes the tripping-coil of a circuit-breaker, and means responsive to variation of current for causing the branch including" the tripping-coil to have a higher time constant than the other.

6. The combination ofa divided circuit, one branch of which includes the tripping-coil of a circuit-breaker, and means dependent for its action upon variation of current for causing the branch including the tripping-coil to have a different time constant than the other.

In witness whereof I have hereunto set my hand this 18th day of December, 1900.

HENRY M. HOBART.

lVitnesses:

HENRY HAsrnn, W OLDEMAR .IIAUPT. 

